Reduce Docker image size, set error handler in build script

Dockerfile

@@ -1,14 +1,21 @@
 FROM node:21-slim AS builder
-ARG MATRIX_TOKEN
-ARG PACKAGE
-ENV PACKAGE ${PACKAGE}
 WORKDIR /code
 COPY . .
-RUN echo "building ${PACKAGE}... "; \
+RUN set -e; \
+    echo "building ${PACKAGE}... "; \
     yarn install; \
     echo "yarn install done. Building...." ; \
     yarn build; \
     echo "building ${PACKAGE} done."; \
     apt-get update && \
     apt-get clean
+
+FROM node:21-slim
+ARG PACKAGE
+ENV PACKAGE ${PACKAGE}
+WORKDIR /code
+COPY --from=builder /code/package.json .
+COPY --from=builder /code/yarn.lock .
+COPY --from=builder /code/node_modules .
+COPY --from=builder /code/packages/core/build/index.js ./packages/core/build/
 CMD yarn run start:js:${PACKAGE}